. >> that is a really great question and sort of as much political science as anything else. anything could big factor. i don't want to sound to nerdly, but the rise of computer-based redistrict teen, strangely enough, that the members of congress and state legislatures have created congressional seats in the house of representatives that are all democratic, all republican. there are relatively few swing seats. we seen a bunch of change in the past couple election, but that's very much the exception rather than the rule. members of the house of representatives fear primaries more than they fear general elections by and large unless they gravitate towards the margins of their parties. that doesn't explain the senate because you can't redistrict the senate, but it has had enormous impact at the state and state legislature level in the more polarized politics we have. i also think the news media plays a role in this. they used to be that there was a kind of shared set of assumptions and news that everybody watched walter cronkite were hotly in brinkley and they sort of made up f